(a) Field of the invention
The invention relates to a beam combiner, and more particularly, to a beam combiner having a high heat-dissipation rate and capable of precisely positioning its members during assembly.
(b) Description of the Related Art
Referring to FIG. 1, a prior beam combiner 100 includes prisms 102, light guides 104 and 106, light sources 108 and reflectors 110. When light emitted from the light sources 108, positioned at opposite sides of the beam combiner 100, directly enters or has been reflected by the reflectors 110 and then enters the light guide 104, it is further directed into the prisms 102 where light is reflected by different surfaces of the prisms and is finally collected in the light guide 106. Thus, a beam combining effect for guiding light emitted from various light sources toward the same output direction is obtained.
In order to acquire the aforesaid beam combining effect, the traveling routes of the input light in the prisms 102 shall follow the optical paths as indicated in FIG. 1. Under the circumstance, end surfaces 104A of the light guides 104 shall not be in contact with input surfaces 102A of the prisms 102. That is, a clearance is necessarily maintained in order to accommodate other media such as air, and thus where, a interface 102A between two media having different refractive index, the total reflection may occur. Hence, when light traveling in the prisms 102 strikes the medium with lower refractive index such as air at any angle greater than its critical angle, the total reflection occurs at the interfaces 102A and light can be reflected to the same direction.
In a prior method, the end surfaces 104A of the light guides 104 adhere to the input surfaces 102A, such that an adhesive would serve as the medium having lower refractive index compared with that of the prism. In another prior method, a supporting member (not shown in the figure) is utilized for directly positioning the prisms 102 and the light guides 104 to further maintain the air clearance 112.
However, heat produced by the high power light sources 108 is prone to deteriorate the adhesive quality and results in the prisms 102 and the light guides 104 unsatisfactory positioning. Furthermore, by using the adhesive for connecting the input surfaces 102A and the end surfaces 104A of the light guides 104, a portion of light tends to escape form the connection surfaces of the adhesive and thus reducing the light coupling efficiency. Also, the space taken up by the beam combiner assembly will be significantly increased if a supporting member is utilized for maintaining the air clearance 112 between the prisms 102 and the light guides 104.
Therefore, an object of the invention is to provide a beam combiner capable of precisely positioning its members and efficiently dissipating heat produced by the light source.
According to the invention, a beam combiner includes a heat-dissipation element and a plurality of rectangular prisms. Each of the prisms is applied with a high-reflection coating for forming a reflective surface, and the prisms are connected to the heat-dissipation element via the reflective surfaces having the high-reflection coatings.
Since the heat-dissipation element is designed to fix the prisms via connecting the reflective surfaces, the occurrence of total reflection is thus ensured by the precise positioning of the prisms keeping in contact with the air medium. As a result, light leak caused by the prisms coming into contact with the light guides or other elements is prevented, and an additional supporting member for positioning the light guides is not required. Besides, the heat-dissipation element having high thermal conductivity is capable of rapidly dissipating heat in the high-reflection coatings, and thus production costs can be reduced because high-quality coatings needed for the endurance of high temperature are no longer required.